A NASA Quest for “Kool”

While members of the astronomical community have for many years used various spectra to study other planets, engineers in the 60s and 70s had only just started applying this technology for studying our own. Once remote sensing instruments were built to do so, it was still difficult to understand and apply the results to plant biology. So forestry had the most to offer Luvall.

"Foresters used aerial photography," he said. "They could identify various coniferous and hardwood stands and measure canopy dimensions and tree heights. I took a course in photogrammetry and learned to use photography from airplanes in surveying and mapping to distinguish objects and identify the sizes, shapes, and positions of photographed objects."

Next, he pursued a master's degree in forest ecology at Southern Illinois. He then took four years off, working at the Savannah River Ecology Laboratory (SREL).

The Savannah River Plant near Aiken, South Carolina, is a 300 square mile Department of Energy reactor facility that, at the time, produced weapons grade plutonium. Starting in 1963, in fact, this plant produced curium-244 as a heat source for space exploration, and in 1985, they began producing plutonium-238 for NASA's deep-space exploration program. Scientists at SREL studied the environmental impacts of reactor operations, including radiation released and thermal impacts of reactor water cooling on stream and lake ecology. While at SREL, Luvall developed techniques for measuring loblolly pine tree transpiration using tritiated water, a radioactive form of water that can be used as a tracer. He also studied cattail response to growing in elevated temperatures in a reactor cooling pond.

In 1980, he entered a PhD program to study tropical forest ecology and microclimatology at the University of Georgia's Institute of Ecology. They sent him to San Carlos, Venezuela.

"It was a tiny village of about 300 people in the middle of nowhere,” Luvall said. “It took 10 days to get there by boat or 2 hours by single engine-plane. It had a military base."

To do research unencumbered by his status as an outsider, he needed to become an accepted part of the San Carlos community. He found an interesting way to gain acceptance.

"The village had a bar and a bakery but no grocery store," he began. "Groups tended to gather near the bar. There were fiestas from time to time in which people would walk down the street singing to collect money for booze. Women would even bring shots of rum out to the walkers. During one such fiesta, I was outside the bar watching the soldiers play a drinking game called 'last man standing.' A couple of them turned to me and said, 'Come on in.' I accepted the invite. At first I pretended to drink from the bottle they handed me, but I didn't swallow. One of the soldiers, noticing my ruse, said 'No no, you have to drink it!' So on the next round, I somehow blew bubbles into the bottle when I feigned a drink. That worked, and they believed I had downed the liquor. Well, I was the last man standing. And after that I never had any trouble with the soldiers as I went about my work."

That work involved using his tritiated water technique to measure the evapotranspiration (ET) rates of tropical rain forest tree species, seedlings, and sprouts in areas where primary forests had been "slashed and burned" into pasture. As the process through which water leaves plants, soils, and other surfaces, ET is a key player in Earth's hydrological cycle. Luvall's findings revealed that ET rates were much higher from stump sprouts than seedlings, but overall ET was greatly reduced when forests were cut.

"The results showed that the destruction of tropical rain forests alters the hydrological cycle, and this meant that the effects of deforestation would be far-reaching," said Luvall.

At that time, tropical forests' impact on the climate had not yet been studied thoroughly, and the critical implications of clearing tropical forests had not really been realized. Soon, NASA would equip Luvall with a unique set of tools to further investigate these effects—from above. But first he had to finish his PhD.

In the early1980s, while continuing to pursue the degree, he worked both as a research associate for the Organization for Tropical Studies North American Office at Duke University and as field administrator for the University of Georgia Man and the Biosphere grant. For this work, he set up a meteorological station at La Selva field station in Costa Rica.

"La Selva was a very Isolated field site in the jungle," said Luvall. "Microwave relay was our only form of communication."

In this setting, he ran a study (still on the ground) to examine the effects of different sized clear cuts of primary and secondary tropical rain forests on ET and soil nutrient leaching. Upon returning to La Selva from his remote field site one afternoon, Luvall found that someone from NASA was visiting and wanted to talk to him.

"Armond Joyce was the division head of a group of scientists at NASA Stennis Space Center," explained Luvall. "He was building a group to start aircraft sensing and study the ecology and physiology of water transport in trees. He encouraged me to apply to NASA for a job after completing my degree."

Luvall's studies plus receiving his PhD in 1984 prepared him for his next steps the following year: that NASA job—and continued research, now with the help of airborne sensors.

Spindly Spires and Airplanes

"Stennis had an optics sensor lab and a Lear 23 Jet," explained Luvall. "They had also acquired TIMS, short for Thermal Infrared Multispectral Scanner, from NASA Jet Propulsion Laboratory. This would be the first use of an airborne multispectral thermal channel."

Standard visual sensors collect only red, green, and blue wavelengths of light, which are within the scope of human vision. Multispectral sensors can detect wavelengths that fall outside this range, including near-infrared radiation, short-wave infrared radiation, and others. The multispectral thermal images show differences in total radiant, or heat, energy emitted from the different objects.

"TIMS was actually developed for geology," Luvall explained. "It was a lab-grade instrument intended for mapping rocks and minerals, and also ideal for our use in studying ET. But at that time there was no formal remote sensing training available, so we had to develop our own ways to calibrate the sensor for atmospheric use. And we learned to use TIMS thermal data to calculate evapotranspiration and characterize ecosystems."

They put their new techniques into use in La Selva, using TIMS along with another new broadband thermal sensor—CAMS, short for Calibrated Airborne Multispectral Scanner. It imaged the radiation temperature of the land surface, while TIMS gathered data within narrower thermal bands, revealing the spectral signatures of objects and materials on the land surface. As these scanners collected land surface thermal (heat) observations, a camera mounted in the aircraft provided false color or natural color stereo aerial photography.

"The camera provided much higher resolution imagery than what we got from the scanners and gave us details needed to help interpret the scanner data," Luvall explained. "Principal investigators like me received the original developed photography and digital data from the scanners. The data was recorded on tapes, and I transferred it to 9-track."

The Lear 23 had no room for passengers, so Luvall never flew on it for his missions. But the platform from which he confirmed and supplemented the airborne sensor data was more harrowing than any airplane ride. He periodically climbed 150 to 200 feet above the ground on two rickety towers upon which he had installed various instruments in and above the tropical rainforest canopy. From these precariously located tools, he gathered data on transpiration from various plant species as well as on meteorological factors like solar radiation, air temperature, relative humidity, and windspeed and direction.

Both towers were in Braulio Carrillo National Park, one in the lowland rainforest and the other at 10,000 ft. elevation in the Volcan Barva Cloud Forest. The "fun" started before he ever reached them. First, he traveled by 4-wheel drive on dirt roads 2 ½ hours north of San Jose, Costa Rica. The road ended at the edge of Braulio Carrillo. The rest of the way to the towers was a tough hike up and down hills and across small rivers via single beam foot bridges. Once there, it got harder.

"It [the tower] did not immediately inspire confidence," wrote Moffett in The High Frontier. "Barely twenty inches wide for its entire length, it resembled some sort of narrow radio antenna tower supported by guy wires. Jeff grabbed a rung and began his ascent. After an uneasy pause, … I followed, climbing band over hand.

"After climbing steadily for several minutes, I poked my head above the treetops, 110 feet above the ground. The tower shot still higher. Forty feet overhead, Jeff uncovered a computer affixed to our spindly spire. A solar panel near the computer powered it. Above him, at the very top of the spire, a horizontal pole sported a wind vane, a spinning wind-speed gauge, and sensors I didn’t recognize. Feeling like one ant passing another on a narrow twig, I squeezed by Jeff to take a closer look. From the pole the tallest tree crowns billowed fifty feet below. The ascent had been equal to scaling a sixteen-story building—without the building."

On this trip, a storm approached, so they hastily descended the tower. They decided to try again at 2:30 a.m. "to catch the sunrise."

"Groggily, we rose in darkness," wrote Moffett. "Sliding along muddy slopes on an unlighted logging road, our Jeep felt like a toboggan, making the trip as stomach-churning as the climb down the tower had been in the rain. We could see only a fraction of the road at any one time in the narrow head light beams. … The Jeep careened back and forth, barely under control despite the four-wheel drive and chains on the tires.

"Our arrival at the base of the tower was timely, up we clambered again, this time tied in with mountain-climbing ropes. As we neared the top of the tower, the sun cracked the green horizon like a slice of orange, exquisitely lighting an undulating canopy surface. I imagined the world awash in forest green as it had been centuries ago, before humans became greedy for that miracle material, wood. A few yards below, Jeff made himself comfortable in a chair bolted to the tower. His fingers flew over the computer keyboard. Muttering technical terms, he copied data from the last forty-five days onto a cassette as the canopy rippled far beneath him."

Luvall would use this hard-earned data along with the airborne data to estimate forest canopy ET and model other forest canopy interactions with the atmosphere. At Stennis and later at Marshall Space Flight Center, he served as PI for additional airborne field missions using TIMS, CAMS, and the Airborne Terrestrial Applications Sensor (ATLAS). In these studies, which took place in Costa Rica and other locations, Luvall continued investigating the relationships of forest canopy temperatures and evapotranspiration and developed evapotranspiration estimates for eastern deciduous and tropical rain forests.  This research helped him document energy budgets of tropical forests and many other types of ecosystems on a landscape scale.

Energy budgets involve the exchange of water and energy with the atmosphere. Luvall's insights into energy budgets contributed significantly to understanding the regional climatic effects of deforestation.

And he had more adventures along the way.

Lost in Translation

During one of his studies, there was an active war in Nicaragua, so Luvall tried not to stray over into that country. In fact, he avoided the border entirely. There was no Costa Rican army, but the CIA had training camps in Costa Rica where they trained Contras—members of the counter revolutionary force that sought to overthrow Nicaragua's left-wing Sandinista government.

On a few occasions, soldiers carrying M16s stopped him and searched him. But he only found himself in a really uncomfortable situation once. It started when he was put in charge of making arrangements for getting the Lear Jet into Costa Rica for his own airborne field mission as well as for the mission of a fellow scientist, Tom Sever, had planned.

"I believe I can safely say that the biggest thing I ever took through customs was a Lear Jet," said Luvall. "But it wasn't as simple as it sounds. I had to work through the American Embassy to arrange with the aviation people to clear the flights and bring the plane in. I told them about my project, Sever's project, and where these projects would be flying."

Sever's mission involved using TIMS to find pre-Columbian roads or "footpaths" and settlements that were over 5000 years old. When translators at the Embassy, who were not always accurate, translated "footpaths" as "footprints," it set off a chain of misunderstandings. The press homed in on the word "footprints" and immediately suspected espionage. They asked to meet with Luvall. Suspicion was further aroused when Luvall suddenly left the country.

"My wife was pregnant with our first daughter," he explained. "She was due in March, but I got the call in February that she was already in labor. This was the same day I had agreed to do the interview with the press, but I left anyway. I took an 8-hour taxi ride over the mountains, then flew into Nicaragua. There were anticraft missiles sites there, so I wasn't entirely comfortable. But I made it to the states at 11 p.m. at night, and my wife gave birth the next day."

Back in Costa Rica, meanwhile, student reporters had "given birth" to a fabricated story about the discovery of spy's "footprints." The national paper picked the story up and ran with it.

"The story said I 'fled the country' when I was confronted about the mission," said Luvall.

Despite the confusion, things ended well. Not only was Luvall proud father of a healthy baby girl, but he also straightened out the "footprint" misunderstanding. The fully legitimate data collection, both from the aircraft and the towers, went smoothly.

Hot Town

After studying forests, a logical next move for Luvall was to use thermal remote sensing to analyze other landscapes. In the late 90's, Luvall and his late friend and colleague Dale Quattrochi documented patterns of heat formation in large metropolitan centers and showed the importance of trees in keeping cities cool.

Urbanization creates urban heat islands—areas with warmer temperatures than nearby rural areas. As a city grows, trees are cut down to make room for commercial development, roads, and suburban growth. Forest growth typically reduces the amount of heat and smog generated by populated areas. Not only do trees provide shade, but all plants use energy from the sun to transpire water during the day, thus cooling the air rather than heating it as do artificial materials.

In Atlanta, Georgia, commercial and suburban development dramatically increased between 1973 and 1992, and nearly 380,000 acres of forest were cleared to accommodate that growth. The materials used to build over forests like these compound the urban overheating problem. Asphalt roads, tar roofs, and other dark, heat-absorbing materials hold in heat long after the sun sets, keeping cities hotter for longer periods of time.

In 1997, Luvall and Quattrochi enlisted the help of Atlanta school children to take ground data on surface temperatures in and around Atlanta at the same time that the ATLAS sensor in the Lear 23 recorded surface temperature data from above. The study identified thermal "hot spots" in metropolitan Atlanta and its suburbs.

"ATLAS, from the belly of the plane, took high resolution thermal photos of the energy given off at the Earth's surface," explained Luvall. "Analysis of the photos showed the amount of heat released by every building, city block, stretch of road, copse of trees—at 10 square meters resolution."

By looking at the amount of reflected energy, they determined how much energy was absorbed and re-radiated by the respective surfaces. In this way, Luvall and Quattrochi could quantify the effects of various building and roofing materials, trees shading roofs, types of asphalt paving the streets, and more.

Their research also showed that summer temperatures in one 30-day period in downtown Atlanta rose an average of 8-10 degrees F above [the concurrent temperatures of ] outlying suburban and rural areas. And localized weather patterns affected by urban heat island effects influenced formation of at least six thunderstorms over Atlanta during this time.

"During the day, a surface thermal low air pressure dome was created, causing cool air to be pulled in from surrounding areas," explained Luvall. "The wind convergence that resulted created and upward flow, pushing hot air up, triggering the thunderstorms. Not only that, but the higher temps doubled the occurrence of chemical reactions that crates surface ozone, which contributes to smog."

Building on the Atlanta research, Luvall served as principal investigator of a U.S. Environmental Protection Agency funded project to quantify the urban heat island effect for Sacramento, California, Salt Lake City, Utah, and Baton Rouge, Louisiana. Again, Luvall and Quattrochi gathered urban heat island data with the help of school children and the ATLAS sensor. The students in Salt Lake City were organized into an urban heat island educational program called “Kool Kids." They dubbed Luvall "Dr. Kool," and the moniker stuck.

In this study, the research duo also investigated how strategically located urban forests and the use of reflective surfaces in construction could help cool cities, reduce energy bills, decrease pollution, and ameliorate further decline of air quality. In Salt Lake City and Sacramento, for example, their work identified areas that needed trees, and local nonprofit tree foundations initiated tree planting projects.

Dr. Kool's quest had come full circle. The answers he had found were now being put to practical use—helping humankind.

As a result of this work and similar projects in the late 90s through early 2000s, Dr. Kool and Quattrochi gained notoriety.

"We drew a lot of news coverage across the country, and did live interviews several times," said Luvall. "There were many magazine and newspaper articles, including a New York Times article about our work. Then they forgot about us."

Except they didn't.

In 2015, both Luvall and Quattrochi received the American Meteorological Society’s Helmut E. Landsberg Award.  The citation reads, “For original contributions and leadership in using high-resolution thermal remote sensing data to understand the urban heat island effect and its environmental consequences."

Carry On

With the launch of ECOSTRESS, short for ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station, high-resolution thermal data became available globally for most major urban areas. Interest has been rekindled in cool roofs, tree planting, and other counter measures championed 25 years ago by Luvall and Quattrochi  to combat urban heat island effects. And younger researchers on quests paralleling Luvall's now turn to him for guidance.

Lucky for them he kept all of his old data. Over 35 years' worth of images and data in various formats are stashed in his office along with crates of flight logs, data calibration details, readme files, technical reports, pre-online publications, and newspaper articles. In short, Luvall is proprietor of a 1 terabyte treasure trove—albeit in vintage formats.

"These photos and data provide a historical point in time to assess change in the regions we covered, so they're even more valuable now than when originally collected," he explained.

But first they need to be transformed into useable form. Enter Stephanie Wingo, 30-year-old data scientist at the Marshall Center. As deputy lead for the Airborne Data Management Group (ADMG), she hunts such treasures as Luvall's. Her group seeks out data from NASA's airborne and field observations and ensures it is archived in NASA's Distributed Active Archive Center (DAAC). Wingo is also working on a web-based Catalog of Archived Suborbital Earth Science Investigations (CASEI) to make vintage airborne data like Luvall's easy to access, along with rich contextual information.

"In the 80s and 90s, there was no DAAC for all this data and imagery," said Wingo. "For his missions, Jeff was the repository."

Neither were there any standard procedures for collecting, converting, and saving data, but Luvall had recognized the importance of preserving it.

"I copied it all," he said. "Now the data is on CDs in ELAS (Earth Resources Laboratory Applications Software) binary format. I converted the original data over the years to this media. There were so many steps behind the scenes for these missions. For example, when an instrument images the Earth's surface, the atmosphere distorts the signal. This distortion has to be corrected before the data can be used. I was forced to understand the instrument and how to do the atmospheric corrections."

"Just wow," Wingo interjected. "We take all that for granted. Now people click a key and get a dataset. We will make sure all the information Jeff painstakingly preserved will be as easily accessible to everyone from now on."

Luvall seems to feel a sense of urgency to ensure that the data and research findings are available to next generation scientists. There's a reason for this.

A few years ago, he was diagnosed with chronic lymphocytic leukemia, documented as resulting from radiation and chemical exposure from his early work at the Savannah River Plant. The disease's progress has stabilized and doesn’t seem to have slowed him much. He no longer scales insubstantial 200-foot towers, but he continues the quest.

Luvall is the NASA Mission Application Representative for the Surface Biology and Geology (SBG) mission (formerly HyspIRI), a planned global NASA Hyperspectral/multispectral thermal satellite mission with global coverage. In this role he provides expert scientific advice on applications use of SBG data and models.

He is also the ECOSTRESS Applied Scientist Co-Lead. Kicking off operation on the space station in 2018 intended for just a one-year mission, ECOSTRESS is still going. It has just been extended for another five years, until September 2028.

But that's not all. Luvall is updating a book he wrote about thermal remote sensing in land surface processes. The first edition published in 2004, and the second edition will publish soon, with the help of ECOSTRESS principal investigator Simon Hook and applications scientists Christine Lee and Kerry Cawse-Nicholson. He plans to feature the research of next generation scientists in this new edition.

Luvall also spends time with his grandchildren; the 7^th was born on December 7.

The question remains, is Dr. Kool really cool? Well, if devoting your life to saving the planet is cool, then Dr. Kool is downright frosty.

And with Wingo's help, current and future scientists will be able to use his data in new studies to make fresh discoveries—and carry on the quest.